My Alchemy shop is no longer working.

I have a similar problem with the regular consignment shop. It will drop the action our of the queue if the game is paused (or even just barely unpaused), but not if I choose it while the game is running. Was your game on pause? If so, try giving it 5 seconds real time before attempting to stick the action in the queue. I usually cause my sim to take more time to get there so I have enough time to slip it in to their queue and have it blend seamlessly into what they were doing.

I hope this helps. But it could be the seeds, or mods, or PC items, or...

Good luck and let us know what you figure out.